Small GTPases are key molecular switches that bind and hydrolyze GTP in diverse membrane- and cytoskeleton-related cellular processes. Recently, mounting evidences have highlighted the role of various small GTPases, including the members in Arf/Arl, Rab, and Ran subfamilies, in cilia formation and function. Once overlooked as an evolutionary vestige, the primary cilium has attracted more and more attention in last decade because of its role in sensing various extracellular signals and the association between cilia dysfunction and a wide spectrum of human diseases, now called ciliopathies. Here we review recent advances about the function of small GTPases in the context of cilia, and the correlation between the functional impairment of small GTPases and ciliopathies. Understanding of these cellular processes is of fundamental importance for broadening our view of cilia development and function in normal and pathological states and for providing valuable insights into the role of various small GTPases in disease processes, and their potential as therapeutic targets.
Animals ; Cilia ; enzymology ; genetics ; metabolism ; GTP Phosphohydrolases ; metabolism ; Humans

Animals ; Biological Transport, Active/physiology* ; Centrioles/metabolism* ; Cilia/metabolism* ; Mice ; Mice, Mutant Strains ; N-Acetylglucosaminyltransferases/metabolism*

In growing children, growth plate cartilage has limited self-repair ability upon fracture injury always leading to limb growth arrest. Interestingly, one type of fracture injuries within the growth plate achieve amazing self-healing, however, the mechanism is unclear. Using this type of fracture mouse model, we discovered the activation of Hedgehog (Hh) signaling in the injured growth plate, which could activate chondrocytes in growth plate and promote cartilage repair. Primary cilia are the central transduction mediator of Hh signaling. Notably, ciliary Hh-Smo-Gli signaling pathways were enriched in the growth plate during development. Moreover, chondrocytes in resting and proliferating zone were dynamically ciliated during growth plate repair. Furthermore, conditional deletion of the ciliary core gene Ift140 in cartilage disrupted cilia-mediated Hh signaling in growth plate. More importantly, activating ciliary Hh signaling by Smoothened agonist (SAG) significantly accelerated growth plate repair after injury. In sum, primary cilia mediate Hh signaling induced the activation of stem/progenitor chondrocytes and growth plate repair after fracture injury.
Mice ; Animals ; Hedgehog Proteins/genetics* ; Receptors, G-Protein-Coupled/metabolism* ; Cilia/metabolism* ; Cartilage/metabolism* ; Regeneration

Primary ciliary dyskinesia (PCD) is a congenital, motile ciliopathy with pleiotropic symptoms. Although nearly 50 causative genes have been identified, they only account for approximately 70% of definitive PCD cases. Dynein axonemal heavy chain 10 (DNAH10) encodes a subunit of the inner arm dynein heavy chain in motile cilia and sperm flagella. Based on the common axoneme structure of motile cilia and sperm flagella, DNAH10 variants are likely to cause PCD. Using exome sequencing, we identified a novel DNAH10 homozygous variant (c.589C > T, p.R197W) in a patient with PCD from a consanguineous family. The patient manifested sinusitis, bronchiectasis, situs inversus, and asthenoteratozoospermia. Immunostaining analysis showed the absence of DNAH10 and DNALI1 in the respiratory cilia, and transmission electron microscopy revealed strikingly disordered axoneme 9+2 architecture and inner dynein arm defects in the respiratory cilia and sperm flagella. Subsequently, animal models of Dnah10-knockin mice harboring missense variants and Dnah10-knockout mice recapitulated the phenotypes of PCD, including chronic respiratory infection, male infertility, and hydrocephalus. To the best of our knowledge, this study is the first to report DNAH10 deficiency related to PCD in human and mouse models, which suggests that DNAH10 recessive mutation is causative of PCD.
Humans ; Male ; Animals ; Mice ; Semen/metabolism* ; Dyneins/metabolism* ; Cilia/metabolism* ; Mutation ; Ciliary Motility Disorders/genetics*

Objective: To investigate the function of primary cilium as an oxygen sensor in PC12 cells. Methods: The PC12 cells were transfected with IFT88 siRNA. The nuclear translocation of hypoxia inducible factor-1α (HIF-1α), nuclear factor erythroid-2 related factor 2 (Nrf2), and ciliogenesis were observed by immunofluorescence staining; and the mRNA expressions of HIF-1α, Nrf2, vascular endothelial growth factor (VEGF) and superoxide dismutase (SOD) were detected by real-time RT-PCR. Results: The ciliogenesis was inhibited in PC12 cells transfected with IFT88 siRNA. In hypoxia group and scramble control group, nuclear translocations of HIF-1α and Nrf2 were observed and mRNA expressions of HIF-1α, Nrf2, VEGF were increased, and those of SOD were decreased. While in PC12 cells transfected with IFT88 siRNA, nuclear translocations of HIF-1α and Nrf2 were not observed, and mRNA expressions of HIF-1α, Nrf2, VEGF were inhibited, and mRNA expression of SOD was increased. Conclusion: Primary cilia may act as an oxygen sensor to transfer the information related to hypoxia and oxidative stress into cells, activating intracellular defense mechanism against the hypoxic injuries.
Animals ; Cilia ; metabolism ; Gene Expression Regulation ; drug effects ; Oxygen ; metabolism ; PC12 Cells ; Rats

Primary ciliary dyskinesia (PCD) is a highly heterogeneous recessive inherited disorder. FAP54, the homolog of CFAP54 in Chlamydomonas reinhardtii, was previously demonstrated as the C1d projection of the central microtubule apparatus of flagella. A Cfap54 knockout mouse model was then reported to have PCD-relevant phenotypes. Through whole-exome sequencing, compound heterozygous variants c.2649_2657delinC (p. E883Dfs*47) and c.7312_7313insCGCAGGCTGAATTCTTGG (p. T2438delinsTQAEFLA) in a new suspected PCD-relevant gene, CFAP54, were identified in an individual with PCD. Two missense variants, c.4112A>C (p. E1371A) and c.6559C>T (p. P2187S), in CFAP54 were detected in another unrelated patient. In this study, a minigene assay was conducted on the frameshift mutation showing a reduction in mRNA expression. In addition, a CFAP54 in-frame variant knock-in mouse model was established, which recapitulated the typical symptoms of PCD, including hydrocephalus, infertility, and mucus accumulation in nasal sinuses. Correspondingly, two missense variants were deleterious, with a dramatic reduction in mRNA abundance from bronchial tissue and sperm. The identification of PCD-causing variants of CFAP54 in two unrelated patients with PCD for the first time provides strong supportive evidence that CFAP54 is a new PCD-causing gene. This study further helps expand the disease-associated gene spectrum and improve genetic testing for PCD diagnosis in the future.
Mice ; Animals ; Humans ; Male ; Kartagener Syndrome/metabolism* ; Cilia/metabolism* ; Semen ; Genetic Testing ; RNA, Messenger ; Mutation

Cilium, an organelle with a unique proteome and organization, protruding from the cell surface, generally serves as a force generator and signaling compartment. During ciliogenesis, ciliary proteins are synthesized in cytoplasm and transported into cilia by intraflagellar transport (IFT) particles, where the inner counterparts undergo reverse trafficking. The homeostasis of IFT plays a key role in cilial structure assembly and signaling transduction. Much progress has been made on the mechanisms and functions of IFT; however, recent studies have revealed the involvement of IFT particle subunits in organogenesis and spermatogenesis. In this review, we discuss new concepts concerning the molecular functions of IFT protein IFT25 and how its interactions with other IFT particle subunits are involved in mammalian development and fertility.
Animals ; Biological Transport ; Carrier Proteins/metabolism* ; Cilia/metabolism* ; Flagella/metabolism* ; Male ; Mammals/metabolism* ; Organogenesis ; Proteins/metabolism* ; Signal Transduction

The experiments of this study was performed to investigate the effects of sulfur dioxide on the changes of glycoconjugates of respiratory system of the rat. Sprague -Dawley male rats weighing about 200 ~250g were divided into a control group and SO2 exposed groups. Again SO2 exposed groups were divided into 10 ppm, 25 ppm, 50 ppm, 100 ppm and 200 ppm subgroups according to concentrations of SO2 and each SO2 exposed groups were divided into 1, 3 and 6 hours groups. For the histological changes, H -E(hematoxylin -eosin) and PAS(periodic acid Schiff) staining were used and to investigate the change of sugar residues of glycoconjugates, biotinylated lectins(DBA, SBA, PNA, BSL -1, sWGA, UEA -1, LCA and Con A) were applied. Generally, the effects of SO2 on the rat nasal respiratory region were more serious at the high concentrations. Moreover, as the exposed time was longer even at the low concentrations, the effects of SO2 were similar to those of high concentration. Compared with all SO2 concentrations, the longer exposed time was, the more serious the effects of SO2 were. In the SO2 exposed groups the binding of PNA, RCA -1 and UEA -1 of cilia in the nasal septal respiratory epithelium tended to increase in the 10 ppm and 25 ppm SO2 exposed groups but it tended to decrease in the 100 ppm and 200 ppm SO2 exposed groups. In the cytoplasm of columnar cells of nasal septal respiratory epithelium, Con A binding increased in all the SO2 exposed groups. In the goblet cells DBA, SBA, PNA, RCA -1 and UEA -1 binding increased remarkably in the 50 ppm SO2 exposed groups but it decreased largely or disappeared in the 100 ppm and 200 ppm SO2 exposed groups. The binding of SBA, PNA, BSL -1, UEA -1 and Con A in the intraepithelial mucous cells which were not detected in the control group, increased in the 25 ppm and 50 ppm SO2 exposed groups while it tended to decrease in the 100 ppm and 200 ppm SO2 exposed groups. The binding of sWGA increased according to the concentrations of SO2 were higher and exposed times were longer. In the superior nasal septal gland, the binding of PNA increased in the 50 ppm and 100 ppm SO2 exposed groups and that of Con A increased in the 25 ppm and 50 ppm SO2 exposed groups. In the inferior nasal septal gland, except for LCA, the binding of the other lectins increased remarkably in the 25 ppm and 50 ppm SO2 exposed groups but it tended to decrease in the 100 ppm and 200 ppm SO2 groups. In the mucous duct cells, the reaction of PNA and RCA -1 increased compared with that of the control group. And the reaction of BSL -1 and UEA -1 increased in the lower concentrations of 50 ppm SO2 exposed group but it decreased in the 100 ppm and 200 ppm SO2 exposed groups. The binding of Con A increased in the 25 ppm and 50 ppm SO2 exposed groups. Consequently, from the results above mentioned that SO2 affected serious changes on glycoconjugates metabolism in the nasal cavity.
Animals ; Cilia ; Cytoplasm ; Glycoconjugates* ; Goblet Cells ; Humans ; Lectins ; Male ; Metabolism ; Nasal Cavity* ; Rats* ; Respiratory Mucosa* ; Respiratory System ; Sulfur Dioxide

OBJECTIVETo construct a mammalian expression plasmid of the BC022687 gene and investigate the expression and localization of the fusion protein in Chinese hamster ovary (CHO) cells.

METHODSThe BC022687 coding sequence was amplified by polymerase chain reaction (PCR) and subcloned into the pEGFP-C1 vector carrying the gene of green fluorescence protein (GFP). After the target region was sequenced, the recombinant plasmid was transfected into CHO cells, and its expression in the CHO cells was determined by Western blot. The localization of GFP-tagged BC022687 in the CHO cells was observed by laser scanning confocal microscopy.

RESULTSBC022687 was successfully cloned into the mammalian expression vector pEGFP-C1, with the restriction fragment length of 950 bp. The expression of the fusion protein was confirmed, with the relative molecular weight of 64 000. The GFP-tagged BC022687 protein was mainly localized in the cytoplasm, and also presented in the centrioles in the transfected CHO cells.

CONCLUSIONThe successful construction of the plasmid expressing BC022687 in CHO cells has laid a foundation for further studies on the role of this protein in ciliogenesis.

Animals ; CHO Cells ; Centrosome ; metabolism ; Cilia ; metabolism ; Cricetinae ; Cricetulus ; DNA, Complementary ; Genetic Vectors ; Male ; Mice ; Plasmids ; Recombinant Fusion Proteins ; genetics ; Transfection

Obesity has become a common healthcare problem worldwide. Cilia are tiny hair-like organelles on the cell surface that are generated and anchored by the basal body. Non-motile primary cilia have been considered to be evolutionary rudiments until a few decades, but they are now considered as important signaling organelles because many receptors, channels, and signaling molecules are highly expressed in primary cilia. A potential role of primary cilia in metabolic regulation and body weight maintenance has been suspected based on rare genetic disorders termed as ciliopathy, such as Bardet-Biedl syndrome and Alström syndrome, which manifest as obesity. Recent studies have demonstrated involvement of cilia-related cellular signaling pathways in transducing metabolic information in hypothalamic neurons and in determining cellular fate during adipose tissue development. In this review, we summarize the current knowledge about cilia and cilia-associated signaling pathways in the regulation of body metabolism.
Adipose Tissue ; Alstrom Syndrome ; Bardet-Biedl Syndrome ; Basal Bodies ; Body Weight Maintenance ; Cilia* ; Delivery of Health Care ; Energy Metabolism* ; Hedgehogs ; Metabolism ; Neurons ; Obesity ; Organelles ; Wnt Signaling Pathway